The present invention relates to a swimming flipper, and in particular to a flipper in which at least one blade portion shows a certain degree of controlled flexibility with respect to the shoe of the flipper itself.
In flipper swimming the thrust obtained by means of the flipper is not due to the whole movement made by the swimmer""s foot, but only to the stage in which his/her leg is bending. The other stage, known as passive stage, therefore causes an extra labour for the diver, with no advantages from the point of view of movement. This negative aspect is even more evident with commonly used flippers, in which the blade portion is made of a relatively stiffer material; such configuration, though being advantageous on the one hand because it improves the thrusting power of the flipper, increases, on the other hand, the useless expenditure of energy in the so-called passive stage.
Therefore, it has been thought to reduce the diver""s effort considerably during this stage, by conveying a certain degree of controlled flexibility to the flippers, that is to say, by making them flexible only during the passive stage.
In our co-pending U.S. patent application Ser. No. 09/431775 filed on Nov. 2nd 1999 and assigned to the same Assignee, a swimming flipper is described whose blade is hinged onto the shoe so as to show a controlled degree of flexibility.
Another solution concerning this includes two carvings, substantially V-shaped, on each of the lateral ribbings stiffening the blade, said carvings being placed above and below the plane of the blade itself, one opposite the other and arranged so as to create on the blade plane a bending line, which is located near the shoe of the flipper itself, perpendicularly to the longitudinal axis of the flipper. However, the bending control only depends on the power of reciprocal contrast between the sloping surfaces of the carvings, said power being rather limited and therefore effective to a limited degree for this purpose. Moreover, the blade area where the bending takes place is extremely weakened.
The present invention aims at providing a swimming flipper having said controlled flexibility for the blade, without hinging the latter to the shoe, that is to say, without carrying out the sole portion of the shoe and the blade separately and connecting them afterwards.
The object of the present invention is to provide a swimming flipper which includes a shoe portion and a blade portion. The blade portion has upper and lower surfaces. Two ribbings are provided along the outer lateral edges of said flipper, said ribbings having an upper edge above the upper surface and a lower edge below the lower surface of the blade portion, and decreasing height towards the free end of said blade portion, characterised in that two carvings, substantially V-shaped, are provided on each of said ribbings near the shoe portion of said flipper, above and below the plane of the blade portion, said ribbings being placed at a suitable distance and staggered one with respect to the other, so as to create two bending lines for the plane of said blade, and limiting means for the bending being provided on the upper surface of said blade portion of the flipper.
Said carvings are advantageously carried out on each ribbing, placed at a distance one from the other so that the point of maximum depth of one carving corresponds to one of the points of minimum depth of the other carving. In particular, the configuration in which the carving above the blade plane is turned towards the free end of the blade seems to be more effective.
In accordance with another aspect of the present invention, the upper and lower edges of the ribbings are coated along their entire length with beads made of elastomeric material. The elastomeric material ensures the elastic response to the bending movements and therefore reduces the load placed onto the blade portion participating in the movements.